This invention relates to a system for measuring the surface temperature distribution of remote objects above approximately 400.degree. C., such as metals during processing.
Numerous material joining, melting and heat treating processes depend upon precise temperature control for success. Most often, contact temperature sensors such as thermocouples are used when possible, but such sensors only reveal the temperature at discrete locations. Rapidly moving or otherwise inaccessible parts cannot, in general, be instrumented in this manner. Contact sensors may also introduce unacceptable impurities in materials. Radiation pyrometers, such as the present invention, often provide the most practical solution to these measurement problems
Conventional "spot" radiation pyrometers provide an effective and accurate means to remotely measure the surface temperature of small areas and are intended to replace contact sensors where the use of the latter is impractical. These instruments have been commercially available from a number of vendors for decades. Spot pyrometers will yield local temperature measurements of a remote surface and will not reveal variation of temperature over the surface unless the device is scanned over the surface or several pyrometers are used.
Since the early 1970's, a few vendors have offered imaging infrared radiometers (also known as Forward Looking InfraRed scanners or FLIR's) which generate a television-like display of object radiance, i.e. object temperature. These devices typically use cryogenically-cooled, single-element photoconductive or photovoltaic detectors and mechanically-scanned optical axes and operate in the 2-6 and 7-14 micrometer spectral region. Neither spectral band is optimal for accurate temperature measurements of most metals at typical processing conditions since metal emissivity is generally quite low at these wavelengths in comparison to the near-infrared (0.7-2 micrometers). Furthermore, the cooling systems and delicate scanning mechanisms required by most thermal infrared imagers often preclude their use in harsh industrial environments.
The present invention fills the gap in available instrumentation between spot radiation pyrometers and thermal infrared imaging radiometers for high temperature measurement and process control industrial applications.